A colossal self-portrait by “pope of pop” Andy Warhol has sold for $17.4 million at Christie’s in London, doubling pre-auction expectations.

The recently discovered 1967 piece, which measures 1.8 metres square, depicts Warhol with a hand to his mouth in what the auction house called “one of the most representative and iconic images of the artist”.

“It has been an incredibly exciting journey to work with a previously unknown work by Andy Warhol, particularly one with such historic importance,” Francis Outred, head of Post-War and Contemporary Art, Christie’s Europe said. “We are thrilled to have been able to publish this work for the first time in our catalogue and to exhibit it to the public for the first time.

“It drew great admiration both at the exhibition and in the saleroom.”

The painting is one of 11 large-scale self-portraits executed in 1967, a time when Warhol had established himself as the most important figure in the Pop Art movement.

Eight of these works were included in the painter’s retrospective at New York’s Museum of Modern Art in 1989, two years after his death.